Posterior Regeneration Research Articles

Regeneration in the gonochoristic polychaete Ophryotrocha notoglandulata

Anterior and posterior regeneration in both male and female Ophryotrocha notoglandulata Pfannenstiel, 1972 was induced by amputation of parts of the prostomium or caudal segments. Regeneration capacity is identical in males and females. The prostomium is not necessary for caudal regeneration.

Maturation, epitoky and regeneration in the polychaete Eunice siciliensis under field and laboratory conditions

In the gonochoric polychaetous annelid Eunice siciliensis Grube, germ cells only develop in the posterior segments of the worm; these segments subsequently differentiate into an epitokous portion separating at maturity from the infertile body part. As in the Pacific and Atlantic palolo worms, the epitokous portions die some hours after spawning. Laboratory investigations revealed that the anterior parts of spawned worms survive and regenerate genital segments. After a period of at least 8 months, paired gonads are developed in these segments. Gonia proliferating later from the germinal tissue are released from gonadal sacs into the coelomal cavities, where gamete development occurs. A reproductive epitokous portion does not mature and separate until the second year of cultivation; it is followed by caudal regeneration. These facts and the observation that only about 50% of the individuals obtained from samples of coralligene were sexually differentiated, led to the conclusion that E. siciliensis probably has a bi-annual reproductive cycle. Caudal regeneration does not depend on the presence of a prostomia hormone. The ability to form posterior regenerates is inherent to the parapodial segments of all body regions, except for mature genital segments. This is also valid for the formation of morphologically different secondary prostomia. However, for initiation and further promotion of gametogenesis and epitokous development, at least one gonadotropic factor originating from the prostomium is required. Neurosecretory cells within the brain suggest this factor(s) to be of neuro-endocrine nature. Specimens developing secondary prostomia were found both under field and laboratory conditions. In several cases, sexual development took place, and even epitokous portions were separated from such individuals. From this it appears that the gonadotropic functions are re-established by the regenerated prostomia in order to ensure reproduction in individuals accidentally deprived of the anterior end. The possible role of temperature and light as environmental factors involved in the control of normal and regenerative growth, of sexual development and reproduction is discussed.

Action des substances inhibitrice et trophique sur les cycles sécrétoires des neurones de la chaîne nerveuse ventrale au cours de la régénération chez Eisenia foetida Sav. f. typica (Annélide, Oligochète)

The injection of a specific inhibitory substance, of cephalic origin for anterior regeneration, or of caudal origin for posterior regeneration, modifies the course of the secretory cycle of FP + cells of the nevous chain. This disturbance appears as a more or less visible lengthening of the duration of the phases of the cycle; thus, it provokes an important slackening of the regeneration. The administration of trophic substance of caudal origin during cephalic regeneration modifies the secretory cycle completely by suppressing a loading phase of the FP + neurones. On the contrary, the trophic substance of cephalic origin has almost no action upon caudal regeneration.

Caudal regeneration in the absence of a brain in two species of sedentary polychaetes

ABSTRACT Evidence has been obtained showing that unlike the requirements of errant polychaetes studied by other investigators, at least two species of sedentary polychaetes, Branchiomma nigromaculata and Chaetopterus variopedatus can undergo caudal regeneration in the absence of a brain. Both Branchiomma, when maintained in a brainless condition by repeated removal of anterior segments, and Chaetopterus, when rendered brainless by amputation of cephalic segments at a level at which anterior regeneration does not occur, undergo posterior regeneration following removal of caudal segments. Animals maintained in a brainless condition for 7–10 days prior to posterior segment removal undergo normal posterior regeneration. Consequently, it appears unlikely that a circulating brain hormone present at the time of amputation is responsible. Experiments were performed on the extremely long 13th segment of Chaetopterus. An isolated posterior half of segment 13, which possesses ventral ganglia, regenerates both anteriorly and posteriorly, while the anterior half regenerates only anteriorly. That the tissues of the anterior half of segment 13 are competent to regenerate posteriorly was shown by leaving the anterior half of the segment attached to the first 12 segments. Under these conditions posterior regeneration occurred. These experiments suggest that the ventral ganglia rather than the brain are important in posterior regeneration in these species.

Recovery and abscopal effects after inhibitory X-irradiation in earthworm regeneration.

AbstractA seven step series of whole body irradiations beginning with 1,872 R and ending with 20,000 R showed that 10,000 R is not sufficient to block posterior regeneration from the fiftieth segment in the barnyard earthworm, Eisenia foetida but that 20,000 R is completely effective.With partial body irradiation at 20,000 or 30,000 R, if the five segments adjacent to the cut surface are exposed and the rest of the body shielded, there is no regeneration by the end of four weeks when controls have regenerated a mean of 34 segments and a minimum of 23 and stopped forming new ones. At the end of seven or more weeks all the partially irradiated worms had recovered and regenerated up to means of 17.3, 20.0, and even 26.3 segments.An abscopal effect was clearly evident in worms in which the first 40 segments were irradiated and the rest of the body, including the ten segments adjacent to the cut surface, shielded. All such worms regenerated without appreciable delay but markedly fewer segments than the controls. The question then arises as to why regenerating blastemas which are fully competent to regenerate a mean of 25 segments do not continue to proliferate until they have formed about 35 like the controls.

Later stages of regeneration in the Polychaete, Nephtys.

AbstractThe sequence of events in posterior regeneration of the polychaete, Nephtys, has been examined in histological preparations from the fifth day to the end of the third week after amputation, that is from the time when wound healing is complete until several new segments are differentiated. The pygidium forms and begins to differentiate prior to segmentation. The first indication of each new segment is the appearance of a large pair of segmental blood vessels which arise from the vascular complex in the gut wall. Associated with these are fibroblasts, the anlagen of the new septum. Epidermal derivatives develop subsequently, appearing first ventrolaterally, close to the regenerating nerve cord. The mitotic rate appears to be highest prior to the period of maximum segment formation. Visible cell differentation follows, and subsequent growth of segments is primarily by cell enlargement. It appears likely that the blood‐vascular system associated with the gut and the regenerating nerve cord, both of which are disproportionately large in the regenerate, are important for the initiation of new segments.

REGENERATION OF THE ENTEROPNEUST, SACCOGLOSSUS KOWALEVSKII

1. Transverse cuts, which separated the animal into two parts, were made on Saccoglossus kowalevskii. When transsection occurred through the proboscis or collar region, the posterior animal fragment was capable of regenerating lost parts anterior to the amputation surface but the anterior animal portion was not able to replace more posterior parts.2. When amputation was performed behind the branchial region, anterior parts were never formed from the posterior animal portion. However, regeneration of more posterior missing parts was now possible.3. Regeneration occurred either from a direct proliferation of the tissues present at the amputation surface (epimorphosis) or through a remodeling of the anterior portion of the amputated fragment (morphallaxis).4. As the locus of amputation was moved posteriorly, epimorphosis became less common and morphallaxis became the principal method of regeneration. Just behind the branchial region, successful posterior regeneration seemed to be accomplished exclusively through epimorphosis.5. Immediately following amputation, regression often occured from the posterior fragments. If regeneration ensued, regression always preceded morphallaxis but did not precede epimorphosis.

Role of the Supra-œsophageal Ganglion during the Early Stages of Caudal Regeneration in Some Errant Polychætes

THE importance of the nervous system in annelid regeneration has been realized for some years1, and it has emerged that, at least in lumbricid oligochaetes and nereid polychaetes, the supra-œsophageal ganglion secretes hormones that are essential for regeneration2–4. Durchon3 showed that if the supra-œsophageal ganglion of three species of nereid is removed regeneration is retarded. Hubl4 discovered that, in lumbricids, extirpation of the supra-œsophageal ganglion at the same time as a number of posterior segments is removed totally inhibits posterior regeneration, but that if the brain is removed 24–48 hr. after the posterior segments are amputated then posterior regeneration proceeds at the normal rate. There is thus a brief critical period during which the brain exerts its influence in initiating regeneration. Since Durchon extirpated the brain of his animals 24 hr. after amputating the posterior segments, it is not clear if the difference between his results and those of Hubl represents a real difference between lumbricids and nereids, or if it is due to the difference in experimental procedure.

Fenomeni rigenerativi e origine degli elementi germinali inSpirorbis pagenstecheri

Summary Posterior regeneration in the Polychaele Spirorbis pagenstecheri, after abdominal amputation, at the level of asetigerous region, is easily and quickly obtained. Growth and differentiation of the abdominal somites occur together and side by side. Specially cytosexual differentiation, showing a cephalo-caudal gradient of morphogenesis, is very early. Already the first or second day after amputation, there arc oocytes at the second growth stage, in the firsts two somites regenerated. They rise from perivessel neoblasts.

A Theory of Growth Limitation

The theory of growth limitation discussed in this review holds that animals continue to grow by the proliferation of voltage-producing units until, by the summation of these units, whether segments or cells, a critical inhibitory voltage is built up. The formation of these units occurs in distal growing regions, and it is in such terminal zones that the inhibitory voltage finally attains a critical value. Subsequent growth of the segments and of the cells of which they are composed, is usually very great, but it is primarily by cell enlargement, not by cell proliferation. This theory is based on the facts uncovered by a systematic reinvestigation, on a scale never before attempted, of posterior regeneration in an earthworm. It is also supported by a large number of anatomical, bioelectrical, and biochemical facts contributed by previous investigators. These are discussed, together with the relationship of this theory to theories of nutritive competition and of hormone action in the control of growth. In b...

The influence of the nerve in regeneration of the amphibian extremity.

The influence of the nerve in regeneration of the amphibian extremity.

Regeneration in an Indian earthwormPerionyx millardi Stephenson 1915

Regeneration by anterior and posterior substrates (having a single transection each), indicated presence along anteroposterior axis of three morphogenetic regions. (1) A region of unipotential capacity from 16/17 anteriorly, in which all morphologically determined regenerates were cephalic, with a section from 6/7 anteriorly in which regeneration was obtained only anteriorly. (2) A region of bipotential capacity in which morphologically determined regenerates were cephalic or caudal. Apparent directional limitations of bipotentiality enabled recognition of three sections: 17/18 to 22/23 (→ 27/28?) in which regenerates at anterior transections were all cephalic but at posterior transections were cephalic or caudal or cephalocaudal; a long middle section in which all anterior regenerates were cephalic and all posterior regenerates were caudal; a posterior section in which regenerates at anterior transections were cephalic or caudal or cephalocaudal but at posterior transections were all caudal, tentatively bounded by 176/177 and 200/201. (3) A region of unipotential capacity in which all morphologically determined regenerates were caudal. Experiments were not extended to permit recognition of a terminal section in which regeneration would only take place posteriorly.

RELATIONS BETWEEN METABOLISM AND MORPHOGENESIS DURING REGENERATION IN TUBIFEX TUBIFEX I

1. Methods of measuring "rate of localization," "rate of early differentiation," and "rate of later differentiation," during posterior regeneration in Tubifex tubifex have been described.2. A method of measuring oxygen consumption of individual worms has been described.3. Oxygen consumption, as determined according to the above mentioned method and also according to the Warburg manometric method, has been found to proceed at a near normal rate during localization and early stages of differentiation in the first week of regeneration.4. Markedly increased rate of oxygen consumption has been found associated with maximum rate of later differentiation during the second week of regeneration.5. No significant cyanide-sensitive fraction of respiration was found at any stage of regeneration.6. Worms in which regeneration had been inhibited by X-ray treatment showed no increase in oxygen consumption.7. Loss of weight by the starving regenerating worms was found to be almost twice as great as by the intact worms.8. The data have been discussed in terms of a metabolic cost of differentiation, which cost would be at least half as great as the metabolic cost of maintenance of the entire worm.9. It is concluded that the marked increase in aerobic metabolism observed during regeneration in T. tubifex is associated with some process or processes involved in differentiation.

The Differential Action of X-rays on the Anterior and Posterior Regions ofTubifex Tubifex

IT IS well known that posterior regeneration in Tubifex tubifex occurs when it is separated with a knife at any level behind the tenth somite and that, following x-ray irradiation, regeneration is inhibited (Stone, 1932). In this paper experiments are described in which the separation was accomplished by irradiating several somites with an intense collimated beam of soft x-rays, and also some experiments in which irradiation of all the animal caused the death of only the posterior. Methods.—Mud containing the animals was collected at frequent intervals for a period of over a year along the shore of Burnet Woods Lake, near the University, and kept in porcelain pans at room temperature in the laboratory. The animals were removed from the mud just before they were irradiated. After irradiation they were kept in clear water in small Petri dishes or in the depressions of well slides. The work may be conveniently divided into two parts, of which the first is concerned with the irradiation of a very small part o...

Further experiments on the influence of the nerve cord in posterior regeneration in Eisenia and Nereis

Further experiments on the influence of the nerve cord in posterior regeneration in Eisenia and Nereis

ORIGIN OF THE MESODERM AND BEHAVIOR OF THE NUCLEOLUS IN REGENERATION INLUMBRICULUS

Nuclei and Nucleoli in Uninjured Individuals.1. The nuclei and nucleoli of the hypodermal cells are small except in the growing tail region. Here they are enlarged, especially in the cells on the ventral side which are involved in the formation of the new nerve cord.2. Large nucleoli are present in the cells of the setigerous glands near the growing region of the tail. In old segments they are small.3. The gut nucleoli are small in the first twelve segments. They are larger from this region up to twenty or thirty segments from the posterior end. In these segments, they are again small.4. Double nucleoli are occasionally found in the mid-gut, where large nucleoli are present.Origin of New Tissue in Regeneration.5. Double nucleoli and mitoses are found in the intestine for eleven or twelve segments from the wound. In this same region the nucleoli are considerably enlarged.6. Cell proliferation in the old intestine practically ceases between the sixth and seventh days of regeneration.7. Neoblasts metamorphose and migrate to the wound at the anterior end as well as at the posterior end. At least eight or nine segments furnish these cells, the four or five nearest the wound apparently playing the most important part as observed by Krecker.8. The failure of the muscle and nerve cells of the old part to form the corresponding new structures in regeneration is perhaps due to the fact that the cytoplasm of these cells has become highly modified, thus rendering them less susceptible to activation.9. The spindle-shaped cells in the dorsal portion of the bud cavity at the anterior end are derived from the hypodermis and not from the muscles of the old part.10. In both anterior and posterior regeneration the nuclei and nucleoli increase in size in the ectoderm cells in the immediate vicinity of the wound. This enlargement is no more rapid in one part than in another; it continues longer in the ventral cells so that by the second day it is greater there.11. The metamorphosis of the ectoderm is not in all probability due to the proximity of the neoblasts, as supposed by Krecker, but instead to an independent transformation.12. The cells of the setigerous glands in the new bud have large nuclei and nucleoli.13. A feature common to all the cells which take part in the formation of the tissues in the regenerating bud is the presence of large nuclei and nucleoli.14. The amount of nucleolar material present in a cell seems to be an index of the activity of its nucleus both in cell-metabolism and in preparation for cell division.15. In Lumbriculus there is no evidence of any division or even of a clearly defined constriction in any of the nuclei of the gut which contain two nucleoli.16. The presence of two nucleoli in a single nucleus is not a step in amitosis, as many have supposed, but is due to the increase in nucleolar substance beyond the amount which can exist within that particular nucleus as a single droplet.17. The various tissues seem to be derived in the same manner both in anterior and in posterior regeneration.

Studies on regulation. V. The relation between the central nervous system and regeneration in Leptoplana: Posterior regeneration

Studies on regulation. V. The relation between the central nervous system and regeneration in Leptoplana: Posterior regeneration